Illumination device and display apparatus including same

ABSTRACT

A display apparatus is constituted by a planar display device and a planar illumination device therefor. A lowering in light quantity at a periphery of the planar illumination device is prevented by inserting a reflection member, such as a reflection frame, having an inside reflection surface along the periphery of the illumination device, or a combination of a scattering means and a transparent sheet member between the display device and the illumination device. A plurality of the display apparatus may be combined to allow an associate movement thereof so as to constitute a composite display apparatus, such as a head-mount display.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a display apparatus suitable for use ina computer display, a view finder for a video camera, a light valve fora video projector, a head-mount display, etc., and particularly anillumination device for such a display apparatus.

An illumination device can be required to have a specific luminancedistribution depending on its use and is typically required to show auniform luminance distribution, e.g., a two-dimensionally uniformdistribution as desired in a display apparatus. Particularly, displayapparatus including an optical modulation device such as a liquidcrystal device frequently use surface illuminant devices, arepresentative example of which may be one disclosed in JapaneseLaid-Open Patent Application (JP-A) 4-86620.

An image display apparatus, such as a head-mount display (HMD) mayinclude a small-sized liquid crystal display device (LCD) of, e.g., ca.0.7 inch, for which a planar fluorescent lamp has been principally usedas a backlight (i.e., illumination device). The backlight may typicallyshow a luminance distribution having a maximum at its center and fallingtoward the peripheries as represented by a dot and dash line shown inFIG. 1.

As another conventional example of display apparatus requiring anillumination device, a liquid crystal view finder for use in videocamera recorders, etc., will now be described.

FIG. 2 illustrates a manner of illuminating such a liquid crystal viewfinder.

The liquid crystal view finder 101 includes a liquid crystal panel(liquid crystal display device) P of the transmission type fordisplaying various data by utilizing the liquid crystal. The panel isprovided with polarizers 102 and 103 applied to both surfaces thereof.On the backside (illustrated as the lower side) of the liquid crystalpanel P, a cold cathode lamp (illumination device) 105 having an arealsize almost equal to that of the panel P so as to illuminate the panelP. On the front side (illustrated as the upper side) of the panel, avirtual image-focusing optical system 106 is disposed, so that light L1having passed through the liquid crystal panel P reaches human eyes Evia the virtual image-focusing system 106 to recognize the datadisplayed on the liquid crystal panel P.

The light issued from the above-mentioned cold cathode lamp 105 shoulddesirably have a uniform light quantity distribution. For this reason,the cold cathode lamp 105 is provided with surface unevennesses to forma scattering surface 107 whereby the light from the cold cathode lamp105 is scattered.

However, such a cold cathode lamp 105 has not been able to provide auniform light quantity or luminance distribution by the scatteringsurface 107 alone. According to our observation, the luminancedistribution has been found considerably uniform as represented by adashed line A in FIG. 3 such that a quantity I₁ reaching at edges of theliquid crystal panel is only about 30% of a light quantity I₂ reachingthe center. Herein, Y₁ on the abscissa represents the size (width) ofthe image display area of the liquid crystal panel P, and the ordinate Irepresents a light quantity introduced into the NA (numerical aperturedetermined by the entrance pupil and focal length of the opticalsystem), which light quantity is actually in the form of athree-dimensional cone.

Incidentally, the reason why the light quantity I₁ reaching edges of theliquid crystal panel P is low, may be attributable to a factor that aliquid crystal panel P has an areal size almost equal to that of thecold cathode ray tube and the edges of the liquid crystal panel Pcoincide with those of the cold cathode lamp 105 so that light supply tothe panel edges becomes insufficient. On the other hand, the center issupplied with a sufficient quantity of light from the cold cathode lamp105 compared with the edges.

Then, in a case where such a cold cathode lamp 105 is used forilluminating a liquid crystal panel P as mentioned above, there occursan image quality degradation due to a luminance irregularity. Thisdifficulty becomes pronounced for displaying, e.g., an image of a wideangle object taken at a panoramic wide angle.

As a solution to the above-mentioned problem, it has been proposed touse a filter having a non-uniform transmittance distribution by theabove-mentioned JP-A 4-86620. The filter is designed to have atransmittance at the center which is lower than those at edges so as toprovide a transmitted light quantity (corr. to I₂) lower than atransmitted light quantity (corr. to I₁) at edges, thus providing auniform light quantity distribution. According to this method, however,the emitted light quantity per se from the illumination device islowered, thus resulting in a new problem of image quality degradationdue to dark illumination. The method further involves a lowering inelectric power efficiency causing an increased drive cost and difficultand expensive production of the filter, thus being liable to provide anobstacle to practical application.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an illumination devicecapable of moderating a remarkable lowering in luminance that occurs atthe edges or sides thereof to provide illumination light having auniform luminance distribution and also a display apparatus includingsuch an illumination device.

Another object of the present invention is to provide an illuminationdevice capable of providing illumination light having a uniformluminance distribution without remarkably lowering the luminance at thecenter thereof and a display apparatus including such an illuminationdevice.

Another object of the present invention is to provide a displayapparatus capable of preventing a lowering in display image quality dueto ununiform light quantity distribution.

According to an aspect of the present invention, there is provided adisplay apparatus, comprising at least: a liquid crystal display devicefor image display, a backlight for illuminating the liquid crystaldisplay device, and a reflection member having a size almost equal to anouter frame of the liquid crystal display device and disposed insertablebetween the liquid crystal display device and the backlight.

According to the present invention, it is possible to reduce thedifference between the light quantities at the peripheries and thecenter of the backlight by inserting a reflection frame having areflection surface between a liquid crystal display device and abacklight.

Further, according to the present invention, two types of light quantity(luminance) distributions from the backlight by providing two stateswherein the reflection frame is inserted between and retreated frombetween the liquid crystal display device and the backlight.

Further, by providing a position sensor for detecting the position ofthe liquid crystal display device and the backlight and controlling areflection frame support and control mechanism based on the detectionresult, it becomes easy to control the insertion and retreat of thereflection frame.

In a first state in the above instance, the reflection frame may beinserted to provide an increased peripheral quantity. In a second state,the reflection frame may retreat and the backlight may be disclosedclose to the liquid crystal display device so as to prevent the loweringin light quantity at the center. These two states may be appropriatelyrealized.

By using at least two display apparatus, it becomes possible to realizean image display apparatus, such as HMD.

By moving the liquid crystal display devices and the backlights in theat least two display apparatus in association with each other or in aninterlocked manner so that all the display apparatus are in the firststate when the display devices and the backlights are in the firstposition and in the second state when the display device and thebacklights are in the second position, it is possible to provide anoptimum light quantity (luminance) distribution for plural displayapparatus, such as HMD.

According to a second aspect of the present invention, there is providedan illumination device, comprising: a light source, a scattering meansdisposed contiguous to the light source for scattering emitted lightfrom the light source when the emitted light passes the scatteringmeans, and a transparent sheet member disposed contiguous to thescattering means.

As a result, emitted light from the light source is transmitted throughthe diffusion means and the transparent sheet member, and at least aportion of the transmitted light through the sheet member is reflectedby the light emission-side boundary of the sheet member toward thescattering means to be scattered thereat, whereby the directionality andutilization of the emitted light from the light source is improved toprovide a better uniformity of light quantity distribution. Thescattering means may be composed as a member having a surface unevennessor a layer having such a surface unevenness or showing a similar lightscattering function.

According to another aspect of the present invention, there is providedan illumination device, comprising: a light source having a diffusionsurface, and a reflection member disposed vertical to the diffusionsurface along an edge of the diffusion surface and having at least oneinside surface forming a reflecting surface.

According to still another aspect of the present invention, there isprovided an illumination device, comprising: a light source having adiffusion surface, a triangular prism array disposed contiguous to thediffusion surface, and a reflection member disposed vertical to thediffusion surface along an edge of the diffusion surface and having atleast one inside surface forming a reflecting surface.

According to a further aspect of the present invention, there isprovided a display apparatus comprising an illumination device asdescribed above, and a display device illuminated by the illuminationdevice to display various data. In this instance, the illuminationdevice can be designed to have a larger area than the display deviceincluding a marginal surface area outside the display device, saidmarginal surface area is covered with a light-shielding means so as toavoid unnecessary illumination light.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing light quantity distributions of a backlightcomprising a planar fluorescent lamp.

FIG. 2 is an illustration of an optical system including a known displayapparatus.

FIG. 3 is a graph showing light quantity distributions of illuminationdevices.

FIG. 4 is a schematic illustration of a display apparatus according to afirst embodiment of the invention.

FIGS. 5A-5C are schematic views for illustrating an operation of adisplay apparatus according to a second embodiment of the invention.

FIG. 6 is a schematic perspective view of a reflection frame used in theinvention.

FIG. 7 includes schematic views for illustrating an operation of adisplay apparatus according to a first embodiment of the invention.

FIG. 8 is a block diagram showing a system of a display apparatusaccording to a second embodiment of the invention.

FIGS. 9A-9C are schematic views for illustrating an operation of adisplay apparatus according to a second embodiment of the invention.

FIGS. 10A-10C are illustrations of light quantity distributions frombacklights corresponding to positions in a horizontal direction of LCDin a binary image display apparatus.

FIG. 11 is a schematic sectional illustration of an optical systemincluding a display apparatus according to a third embodiment of theinvention.

FIG. 12 is a schematic sectional view for illustrating a function of thethird embodiment.

FIG. 13 is a schematic sectional view for illustrating a function of adisplay apparatus according to a fourth embodiment of the invention.

FIG. 14 is a schematic sectional view of an optical system including adisplay apparatus according to a fifth embodiment of the invention.

FIG. 15 is a schematic sectional view of an optical system including adisplay apparatus equipped with a surface illuminant device.

FIG. 16 is a schematic perspective view of a planar illuminant deviceaccording to the sixth embodiment of the invention.

FIG. 17 is a view for illustrating an operation principle of the planarilluminant device according to the sixth embodiment of the invention.

FIG. 18 is a graph illustrating light quantity distributions from planarilluminant devices.

FIG. 19 is a schematic sectional view of a planar illuminant deviceaccording to a seventh embodiment of the invention.

FIG. 20 is a schematic sectional view of an optical system including adisplay apparatus according to an eighth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an illumination device including a lightsource and an improved optical system by which a non-desirable lightquantity decrease (luminance lowering) at light source edges (sides) isprevented.

An example of the improved optical system is given by a reflectionmember for increasing the luminance at the light source edges.

In a case where the light source is in the form of a quadrangleinclusive of a square and a rectangle and is desired to issue a uniformplanar illumination light, the reflection member may preferably be inthe form of a frame encircling four sides, of which all the innersurfaces may desirably constitute reflecting surfaces. However, in acase where a luminance lowering for only one side is desired to beprevented, the reflection member may assume a wall-like member disposedalong one side.

The reflection members may be formed by a frame-shaped or a wall-shapedsubstrate coated with a metal or dielectric laminate film so as toprovide a reflecting surface. The substrate may comprise a transparentor opaque material, such as glass or plastic, and may preferablycomprise a molded plastic of, e.g., acrylic resin or polycarbonate fromthe viewpoint of easiness of shaping.

Another example of the improved optical system used in the presentinvention may be constituted by a combination of a scattering sectionand a transparent sheet member.

Some specific embodiments of the present invention will now bedescribed.

(First Embodiment)

FIG. 4 is a schematic sectional illustration of a display apparatusincluding an illumination device according to a first embodiment of thepresent invention.

The display apparatus includes a LCD panel (display device) 101, and abacklight 102 comprising a planar fluorescent lamp. In this embodiment,the illumination device also includes a reflection frame (reflectionmember) having inner surfaces 103a constituting a totally reflectingsurface.

The effect of the reflection frame 103 is as follows. As shown in FIG.4, e.g., light fluxes 111 and 112 from the center of the backlight 102intersect each other on the LCD 101. In order to obtain an identicallight quantity at a periphery, it may be necessary to provide, inaddition to a light flux 121, a hypothetical light flux 122", whichhowever is actually not present. On the other hand, if the reflectionframe 103 is inserted as shown in FIG. 4, a light flux, which goesoutwards in the absence of such a reflection frame 103, is reflected asa light flux 122 as shown. As a result, the light flux 121 and the lightflux 122 intersect each other on the LCD 101, thereby providing a lightquantity similar to that at the center.

An improved luminance distribution obtained in the above-describedmanner may be represented by a solid line in FIG. 1.

(Second Embodiment)

A display apparatus according to a second embodiment of the presentinvention will be described with reference to FIGS. 5A-5C, 6 and 7.

FIGS. 5A-5C are schematic sectional views of a part of a displayapparatus according to this embodiment in three states in operation.More specifically, the display apparatus shown in FIG. 1 is a binaryimage display apparatus including two identical display apparatusdisposed laterally in combination for use in a HMD. FIGS. 5A-5C shownonly one of the laterally disposed two display apparatus, and the otherone (not shown) is disposed laterally symmetrically with the shown one.More specifically, such a symmetrical mating apparatus (not shown) maybe disposed on a left side of the apparatus shown in FIGS. 5A-5C in casewhere image light from the display apparatus reaches a human eye afteran odd-numbered times of reflection (as shown in FIGS. 9A-9C describedhereinafter) and on a right side of the apparatus shown in FIGS. 5A-5Cin case where image light from the display apparatus reaches a human dyeafter an even-numbered times of reflection.

Referring to FIGS. 5A-5C, a shown half of the binary display apparatusincludes a LCD panel (liquid crystal display device) 101 of thetransmission-type, a backlight 102 comprising a planar fluorescent lamp,a reflection frame 103 disposed insertable between the LCD 101 and thebacklight 102, a reflection frame support and control mechanism 104including a supporting member for horizontally supporting the reflectionframe 103 and a position control system therefor, a position sensor 105for detecting the horizontal positions of the LCD 101 and the backlight102, a control circuit 106 for receiving data from the position sensor105 and supplying a control signal to the reflection frame support andcontrol mechanism 104, a LCD unit-moving frame 107 in which the LCD 101and the backlight 102 are moved horizontally thereon, and abacklight-supporting member 108 for supporting the backlight 102 in adirection toward and away from a viewer, i.e., a vertical direction inthe figure.

The LCD 101 is of the transmission type and is designed to be observedfrom an upper point (in the figure) with a transmitted portion of lightissued from the upper emission surface of the backlight 102. The LCD 101and the backlight 102 are horizontally moved in an interlockedrelationship, i.e., integrally while retaining a relative position witheach other, though it is not illustrated specifically. In other words,the LCD 101 and the backlight 102 constitutes a unit which moves in ahorizontal direction, i.e., in a transverse direction in the figure,within the LCD unit-moving frame 107.

The reflection frame 103 is desired to have an inner side forming analmost totally reflecting surface 103a, e.g., covered with a silverplating layer. The reflection frame 103 has a size conforming to theouter frame of the LCD 101. The reflection frame 103 is held to have afixed position in a direction toward the viewer (i.e., in a verticaldirection in FIGS. 5A-5C) and controlled to move horizontally in FIGS.5A-5C by the reflection frame support and control mechanism 104.

Now, some description will be made regarding a HMD constituted by adisplay apparatus according to the invention.

It has been practiced to use a binary image display apparatus includingtwo (systems of) display apparatus, such as a so-called HMD (head-mountdisplay) mounted on a human head, for enlarging and projecting images oftwo display devices into the air through the respective optical systemsso that the resultant image is observed as a virtual image by theviewer. According to this type of image display apparatus, it ispossible to view a stereoscopic image, a wide-angle image, or aso-called panoramic image.

FIG. 8 is a block diagram of an example of such a HMD proposed by ourresearch and development group. Referring to FIG. 8, the HMD apparatus1100 includes a display unit 1101 for a right eye, a display unit 1102for a left eye, and image signal input terminals 1103 and 1104 and aphotometric data input terminal 1105 for receiving image data signalsand photometric data signals from a compound eye camera (not shown). Theright eye display unit 1101 includes a LCD 1106 for displaying imagesfor a right eye and an optical system 1107 including lenses, etc., andthe left eye display unit 1102 includes a LCD 1108 for displaying imagesfor a left eye and an optical system 1109 including lenses, etc. In thisway, images for right and left eyes are respectively displayed by usingtwo LCDs.

FIGS. 9A-9C illustrate operations of such an image display apparatus fordisplaying a stereoscopic image, a wide-angle image or a panoramicimage. For displaying a stereoscopic image, LCDs 1106' and 1108' (asdisplay devices) and mirrors 1107' and 1109' (as optical systems) aredisposed as shown in FIG. 9A so that two virtual display images forright and left eyes can be fused in the head of a viewer.

On the other hand, for displaying a panoramic image, the display devicesand optical systems are disposed as shown in FIG. 9C so that two virtualimages for the right and left eyes can be laterally joined in the headof a viewer.

Further, by disposing the display devices and optical systems atintermediate positions as shown in FIG. 9B which is intermediate betweenFIGS. 9A and 9C, a left-side portion of a virtual display image for aright eye and a right-side portion of a virtual image for a left eyeoverlap each other so that the viewer recognizes the overlapping portionas a stereoscopic image and the other portions as a panoramic imagenarrower than in the case of FIG. 9C.

Representative examples of dispositions of the display devices andoptical systems for displaying a stereoscopic image, a wide-angle imageand a panoramic image have been described with reference to FIGS. 9A-9Cbut their dispositions are not so determinative in a single way. Morespecifically, the display devices and optical systems can be arbitrarilymoved in a lateral direction to arbitrarily set a stereoscopic orpanoramic degree of image. The control can be performed manually by aviewer depending on the kind of display image or automatically by addinga discrimination signal to an image data signal for discriminatingwhether the image is a stereographic image or a panoramic image, etc.

In the image display apparatus according to the present inventionconstituted in the above-described manner, an initial position may be astereographic image display position as shown in FIG. 9A wherein theleft and light images are horizontally in alignment. This position isnot necessarily limited for displaying a stereographic image but mayalso be adopted in the case of displaying an identical image on bothleft and right display apparatus. This state corresponds to a positionas shown in FIG. 5A wherein the unit of the LCD 101 and the backlight102 is moved to one side end of the LCD unit-moving frame 107. The unitposition is detected by the position sensor 105 and, based on thedetected position, the reflection frame 103 is set to be positioned atthe other side end by the reflection frame support and control mechanism104. Further, the backlight 102 is caused to approach the LCD 101 by thebacklight-supporting member 108.

A panoramic-stereographic mixture image display position as shown inFIG. 9B where the left and right images partially overlap each other,corresponds to a position as shown in FIG. 5B. When the unit of the LCD101 and the backlight 102 comes to a position as shown in FIG. 5B, basedon the detected position, the backlight 102 is caused to retreat fromthe LCD 101. Then, the reflection frame 103 is inserted between the LCD101 and the backlight 102 by the reflection frame support and controlmechanism 104. The position of the reflection frame 103 is determined tocorrespond to the outer frames of the LCD 101 and the backlight 102,respectively. The position may be set to a position where the lightquantity to the overlapping portion of the left and right images beginsto fall, i.e., at a position close to the position represented by asecond left vertical dash line in FIG. 1. When the unit arrives close tothis position from the position shown in FIG. 5A, the position sensor105 operates to initiate the above-mentioned operations.

From the position shown in FIG. 5B to the position shown in FIG. 5C, thereflection frame support and control mechanism 104 effects a control soas to retain the aligned positional relationship among the LCD 101, thebacklight 102 and the reflection frame 103.

The positional relationships among the LCD 101, the backlight 102 andthe reflection frame 103 are illustrate in summary by three figures inFIG. 7. FIG. 7 is drawn so that the device is seen from a rightwardposition. The backlight 102 is moved instead of the LCD 101 because theoptical system is controlled to focus on the LCD 101 and the focusingstate is retained by not moving the LCD 101.

As is shown in FIG. 1, by the insertion of the reflection frame 103, thelight quantity ratio between the periphery and the center increases fromca. 60% before the insertion to ca. 80-90% after the insertion, thusimproving the light quantity irregularity. On the other hand, as thedistance between the backlight 102 and the LCD 101 is increased by theinsertion of the reflection frame 103, the entire luminance level can besomewhat lowered. Such a lowering in luminance is obviated at the timeof stereoscopic image display as shown in FIG. 5A by causing thereflection frame 103 to retreat from the inserted position and causingthe backlight 102 to approach the LCD 101. FIGS. 10A-10C show luminancedistributions at the three positions shown in FIGS. 5A-5C, respectively.In FIGS. 10A-10C, the distributions denoted by PRA represent thoseobtained by a prior art apparatus and the distributions denoted by INVrepresent those obtained by this embodiment of the present invention.

In this embodiment, the reflection frame 103 has been inserted at allperipheral sides of the backlight 102. A particular problem to beconcerned in this type of image display apparatus, however, is a lightquantity decrease at the periphery on at least one side where the leftand right images overlap each other, so that it is possible to dispose areflection member (wall-like member) only along such one side.Incidentally, the above-mentioned unit of the LCD 101 and the backlight102 can be moved manually or automatically by adding a discriminationsignal to image signals and by recognizing such a discrimination signal.

In the above-described embodiment, a reflection frame 103 having aninside surface constituting an almost totally reflecting surface isinserted between a backlight 102 and a LCD 101 when the unit of thebacklight 102 and the LCD 101 is at a horizontal position for apanoramic image display or a panoramic-stereoscopic mixture imagedisplay, thereby obviating a peripheral light quantity decrease of thebacklight 102. As a result, it becomes possible to obviate an imagequality degradation at the time of a panoramic image display or apanoramic-stereoscopic mixture image display due to a luminancedistribution irregularity of the backlight 102 while obviating aremarkable luminance lowering at the center. Further, when the unit ofthe LCD 101 and the backlight 102 is at a horizontal position for astereoscopic image display, the reflection frame 103 is removed, and thebacklight 102 is caused to approach the LCD 101 to prevent the loweringin luminance at the center, thereby preventing an image qualitydegradation of a stereoscopic image.

As described above, according to this embodiment, a reflection framehaving a reflecting surface is inserted between a LCD and a backlight toreduce a difference in light quantity between a periphery and the centerof the backlight, thereby providing a good image free from luminanceirregularity.

Further, by selecting an insertion position and a retreat position ofthe reflection frame, it is possible to realize two types of lightquantity distribution of the backlight.

Further, by disposing a position sensor of the LCD and the backlight andcontrolling a reflection frame support and control mechanism based onthe position detection result, it becomes easy to control theinsertion-retreat control of the reflection frame, thereby ensuring aproper operation of the apparatus.

In a first state, the reflection frame may be inserted to reduce thelight quantity difference between a periphery and the center of thebacklight. In a second state, the reflection frame is caused to retreatand the backlight is brought in proximity to the LCD so as to reduce thelight quantity decrease at the center. In this way, it is possible toprovide an optimum backlight illumination condition as desired.

Further, by using at least two systems of display apparatus, it ispossible to realize an image display apparatus, such as an HMD.

Further, by providing plural display apparatus each including a LCD anda backlight therefor and moving the plural display apparatus inassociation with each other so as to select a first position where allthe display apparatus are placed in a first state or a second positionwhere all the display apparatus are placed in a second state, it ispossible to provide an optimum light quantity distribution of lightsource for a composite image display apparatus, such as an HMD.

(Third Embodiment)

A third embodiment of the present invention will now be described withreference to FIGS. 11 and 12.

Referring to FIG. 11, a liquid crystal view finder (liquid crystaldisplay apparatus) 210 includes a liquid crystal panel (liquid crystaldisplay device) P. The liquid crystal panel P is of the transmissiontype and comprise two-dimensionally arranged pixels and electrodes so asto display various data. The panel P is sandwiched between a pair ofpolarizers 202 and 203 disposed in cross nicols.

The liquid crystal view finder 210 also includes an illumination device211. The illumination device 211 comprises a thin cold-cathode lamp(light source) 205 provided with an upper scattering surface as ascattering member or means 207. Onto the scattering member 207, atransparent polycarbonate plate (sheet member) 212 is adhered, and thepolycarbonate plate 212 is adhered to the lower surface of the polarizer203. In this embodiment, the polycarbonate plate 212 is designed to havea refractive index n of 1.59, and the lower polarizer (a medium on alight-transmitted side of the sheet member) is designed to have arefractive index n' of 1.53. In this embodiment, a total reflectioncondition having a polarizing characteristic may be used as will bedescribed hereinafter, so that a polycarbonate resin plate 212 having agood birefringence characteristic is used so as to provide an improvedtwo-dimensional light quantity distribution.

A liquid crystal panel may provide an asymmetrical angle characteristic(viewing angle characteristic) in contrast distribution due to anasymmetrical characteristic of liquid crystal director orientations. Forthis reason, in this embodiment, a virtual image focusing optical system206 is designed to constitute a telecentric system for guiding principalrays in a direction (Z-direction) normal to the liquid crystal panel Psurface as shown in FIG. 11. In FIG. 11, a total aperture angle (=2arcsin NA) is shown as 2NA. Depending on an illuminance at a retina of ahuman eye E, the pupil size of the eye E is changed to determine aneffective light flux diameter entering the eye E and an effective NA foremission light from the liquid crystal panel P. As the brightnesschanges depending on the kind of image source and in order to facilitatethe adjustment for alignment of the optical axis of the optical systemand the optical axis of the eye E, a light reflux diameter of 6-8 mm maybe required for a pupil of 1-2 mm. For this reason, the illuminationdevice 211 may be evaluated with a light flux corresponding to NA of theoptical system 206.

The function of this embodiment will be described with reference to FIG.12.

Light emitted from the cold cathode lamp 205 is transmitted through thescattering member 207 and the acrylic plate 212 so that it is scatteredat the scattering member 207 and transmitted through the polycarbonateplate 212 in various directions (only a light flux L₂ being shown). Thelight scattering state at this time is determined by the structure ofthe cold cathode lamp 205 and the scattering characteristic of thescattering member. The light flux L₂ transmitted through thepolycarbonate plate 212 is at least partly reflected at the uppersurface (boundary) of the polycarbonate plate 212 toward the scatteringmember 207 (a flux L₄) and at least a part thereof is reflected andscattered at the scattering member 207 (fluxes L₅). The reflectance atthe upper surface of the polycarbonate plate 212 varies depending on theincidence angle θ_(i) of the flux L₂, which will be describedhereinafter. Further, in case where the incidence angle θ_(i) is smallerthan a critical angle θc, a portion (L₃) of the flux L₂ is emittedtoward the liquid crystal panel without being reflected at the uppersurface of the polycarbonate plate.

As a result, a portion of the reflected light and the light L₅ aretransmitted through the upper surface of the polycarbonate plate 212 tobe transmitted through the lower polarizer 203, where linearly polarizedlight is selectively allowed to be transmitted. The linearly polarizedlight transmitted through the lower polarizer 203 enters the liquidcrystal panel P to be subjected to a birefringence effect at respectivepixels depending on a two-dimensional image and converted into a twodimensional image while being transmitted through the upper polarizer202. Of the thus-transmitted light, only a portion within 2NA of theoptical system 206 is guided to the human eyes E to be recognized asdata thereat.

In a conventional apparatus, the scattered light quantity is decreasedat the four sides edge portions of the scattering member 207 by an anglecomponent corresponding to either one NA of the 2NA, thus lowering thelight quantity at peripheries.

On the other hand, this embodiment functions in the following manner. Ofthe forward scattered light L₂ from the scattering member 207, a portionhaving a large scattered angle and therefore a large incidence angleθ_(i) to the upper surface of the polycarbonate plate 212 shows a largereflectance at the upper surface of the polycarbonate plate 212, therebyproviding a larger proportion component L₄ re-incident to the reflectingmember 207 at at a reflection angle θ_(r). Now, if the refractive indexof the polycarbonate plate is denoted by n, the refractive index of amedium on a transmitted side of the polycarbonate plate is denoted by n'(refractive index of the polarizer 203 in this embodiment wherein thepolarizer 203 is directly bonded to the polycarbonate plate 212; that ofan adhesive in case where such an adhesive fills a gap between thepolycarbonate plate 212 and the polarizer 203; or that of air in casewhere a spacing is provided between the polycarbonate plate 212 and thepolarizer 203) and a refraction angle is denoted by θ_(t), the uppersurface of the polycarbonate plate 212 may show amplitude reflectancesr_(s) and r_(p) as follows for S polarized light and P polarized light,respectively:

    r.sub.s =-sin(θ.sub.i -θ.sub.t)/sin(θ.sub.i +θ.sub.t)

    r.sub.p =tan(θ.sub.i -θ.sub.t)/tan(θ.sub.i -θ.sub.t).

Based on the above and the following Snell's law:

n·sinθ_(r) =n'·sinθ_(t),

a large incident angle θ_(i) to the polycarbonate plate 212 provides alarger intensity reflectance Rs (=r_(s) ²) of the S polarized light, thescattered light outside 2NA is preferentially reflected toward thescattering member 207. The intensity reflectance of the P polarizedlight decreases as the incidence angle θ_(i) increases up to theBrewster angle θ₀ given by the following equation, and increasesthereafter.

    tan θ.sub.0 =n'/n.

Further, in case of n>n', a total reflection condition is satisfied whenthe incidence angle reaches a critical angle θc given by the followingequation:

    sin θc=n'/n.

In the range of θ₀ <θ_(i) <θ_(c), a larger θ_(i) provides larger Rp andlarger Rs. In the range of θ_(i) ≧θ_(c), Rp=Rs=1, thus giving notransmitted light.

In the case of the above example wherein n=1.59 and n'=1.53, thereresult in θ₀ =43.9 deg. and θ_(c) =74.2 deg., so that scattered lighthaving an incidence angle of at least ca. 74 deg. is totally reflected.

This embodiment shows the following effects.

In a conventional case having no polycarbonate plate, a light flux asdenoted by L₂ is not incident to a human eye E because of its emissiondirection. According to this embodiment wherein an polycarbonate plate212 is inserted between the liquid crystal panel P and the scatteringmember or surface 207 of the cold cathode lamp 205, however, at least aportion (L₄) of the light flux L₂ is reflected at the upper surface ofthe polycarbonate plate 212 toward the scattering member 207. Theresultant reflected light L₄ is scattered at a peripheral portion of thescattering member 207 and a portion (L₅) of the again scattered light istransmitted through the polycarbonate plate to be incident to aperipheral region of the liquid crystal panel P and guided within the2NA of the optical system 206, thereby entering the human eye E. As aresult, the light quantity entering the peripheral region of the liquidcrystal panel P is increased compared with the conventional case, andthe light quantity distribution is uniformized. A solid line in FIG. 3represents a result of this embodiment based on data measured by uscompared with a result in the conventional case represented by a dashedline in FIG. 3. As shown in FIG. 3, the light quantity entering theperipheral region of the liquid crystal panel P has been remarkablyimproved increased up to 70% of that at the center, thereby providing animproved light quantity distribution. Further, light from the peripheralregion of the cold cathode lamp 205 also re-enters the central region ofthe scattering member 207 and is reflected thereat, so that the lightquantity at the central region I₂ is also slightly increased.

Particularly, in this embodiment, the polycarbonate plate 212 isdesigned to have a refractive index n which is larger than therefractive index n' of the lower polarizer 203, total reflection can beutilized while it depends on the incidence angle θ₁ of the transmittedlight L₂, so that a further uniform light quantity distribution isrealized.

By using such an illumination device 211 for illuminating a liquidcrystal panel P, the image quality degradation of the liquid crystalpanel can be prevented to provide good image qualities even in case ofpanoramic wide-angle images of wide objects such as sky or sea.

Further, the uniformization of light quantity distribution can beperformed without locally decreasing the transmittance or lowering theillumination quantity.

The use of the polycarbonate plate 212 as a transparent sheet member inthis embodiment allows an economical production of the illuminationdevice 211.

(Fourth Embodiment)

A fourth embodiment of the present invention will be described withreference to FIG. 13, wherein members identical to those in FIG. 11 aredenoted by identical numerals, and description thereof will be omitted.

An illumination device 220 according to this embodiment includes a prismarray (prism device) 221 bonded to a polycarbonate plate (transparentsheet member) 212. The prism array 221 is composed of a large number ofmicro-prisms. The prism array 221 (particularly the material thereofdisposed on a light-transmitted side of the polycarbonate plate 212) isdesigned to have a refractive index n' which is lower than therefractive index n of the polycarbonate plate 212. The prism array 221of the illumination device 220 is applied onto a lower surface of alower polarizer 203, a liquid crystal panel P, etc. (not shown) isapplied onto an upper side of the lower polarizer 203 similarly as inthe third embodiment. The micro-prisms constituting the prism array 221are designed to have a refractive index higher than that of air presentbetween the prism array 221 and the polarizer 203.

The function of this embodiment will now be described.

Light emitted from a cold cathode lamp (light source) 205 is scatteredat a scattering member 207 similarly as in the above embodiment. Aportion (L₄) of light flux L₂ transmitted through the polycarbonateplate 212 is reflected at the upper surface of the polycarbonate plate,and another portion (L₃) is transmitted through the prism array 21. Thetransmitted light L₃ is provided with an improved directionalityregarding its illumination direction by the prism array 221. Further, asthe refractive index n' of the prism array is designed to be lower thanthe refractive index n of the polycarbonate plate 212, the light L₂ cancause total reflection depending on the incidence angle. Further,reflected light L₄ from the upper surface of the polycarbonate plate 212is reflected and scattered at the scattering member 207 similarly as inthe above embodiment.

This embodiment shows the following effects.

Transmitted light through the polycarbonate plate 212 is provided withan improved directionality by the prism array 221 to provide anincreased light quantity incident to the human eye E.

Similar effects as in the third embodiment can be obtained. Thus, thelight quantity distribution can be uniformized by the combination of thepolycarbonate plate 212 and the scattering member 207, therebypreventing the image quality degradation of the liquid crystal panel P.Further, the uniformization of light quantity distribution can beperformed without locally decreasing the transmittance or lowering theillumination quantity. The use of the polycarbonate plate 212 as atransparent sheet member in this embodiment allows an economicalproduction of the illumination device 220.

(Fifth Embodiment)

A fifth embodiment of the present invention will be described withreference to FIG. 14, wherein members identical to those in the fourthembodiment are denoted by identical numerals, and description thereofwill be omitted.

A liquid crystal display apparatus 230 includes an illumination device211 and a liquid crystal panel (liquid crystal display device) P, andthe illumination device 211 is designed to have a larger areal size thanthat of the liquid crystal panel P (more specifically the area of theimage display region thereof). A portion of the upper surface of theillumination device 211 outside a region thereof loaded with the liquidcrystal panel P is covered with a frame-shaped light-shielding plate(light-shielding means) bonded thereto, so as to obviate stray light bycutting off unnecessary illumination.

This embodiment shows the following effects.

Only a portion in the central area of light emitted from theillumination device 211 is utilized, so that the light quantity enteringthe peripheral region of the panel is increased compared with those inthe former embodiments, so that the light quantity distribution isfurther uniformized, so that the image quality degradation of the liquidcrystal panel P is prevented at a high level.

Similar effects as in the third embodiment can also be obtained. Thus,the light quantity distribution can be uniformized by the combination ofthe polycarbonate plate 212 and the scattering member 207, therebypreventing the image quality degradation of the liquid crystal panel P.Further, the uniformization of light quantity distribution can beperformed without locally decreasing the transmittance or lowering theillumination quantity. The use of the polycarbonate plate 212 as atransparent sheet member in this embodiment allows an economicalproduction of the illumination device 230.

Incidentally, in the above third embodiment, the refractive index n ofthe polycarbonate plate 212 is designed to be 1.59 and the refractiveindex n' of the lower polarizer 203 are designed to be 1.53. Thesevalues are not essential but can be appropriately determined dependingon the scattering characteristic of the scattering member 207 and thestructure of the cold cathode lamp 205. More specifically, inconsideration of a light quantity distribution in the absence of thepolycarbonate plate 212, in case where a larger difference is presentbetween the central light quantity I₂ and the peripheral light quantityI₁ than the one represented by the dashed line A in FIG. 3, it ispossible to increase the refractive index n and decrease the refractiveindex n' so as to lower the critical angle θ_(c), thereby furtheruniformizing the light quantity distribution. In this instance, it isfurther effective to increase the thickness h of the polycarbonate plate212.

In the above embodiment, the refractive index n of the polycarbonatemember 212 is set to be smaller than the refractive index n' of thematerial (the lower polarizer 203 or the prism array 221) disposed onthe transmitted light side of the polycarbonate member 212. This is nothowever essential. Even in the case of n<n', it is also possible toutilize a reflected portion from the upper surface of the polycarbonatemember even if it is decreased.

The polycarbonate plate 212 used in the above embodiments is notessential. Other plastic materials, such as polystyrene resin, can alsobe used to provide a light and economical illumination device similarlyas in the above embodiments. It is also possible to use broad glass orabraded glass.

Particularly, in the case of adopting a structure wherein a spacing isprovided between a sheet member 212 and a polarizer 203, the sheetmember 212 may preferably comprise an acrylic (resin) plate. An acrylicplate may have a refractive index n of ca. 1.49 in contrast with therefractive index n' of ca. 1.00, thereby providing a critical angleθ_(c) =42.2 deg., so that a very large proportion of light reflux can betotally reflected. Accordingly, the effect of this embodiment can beremarkably exhibited by this structure.

Moreover, an acrylic plate shows a smaller birefringence than apolycarbonate plate and can therefore provide the desired products moreeasily. Further, an acrylic plate is inexpensive.

The liquid crystal view finders disclosed in the above embodiments aredesigned to be not mounted on a human body but can be modified into aform adapted to be mounted on a human body, such as an HMD (head-mounteddisplay) in the form of goggles or a helmet to be mounted on a face or ahead. The HMD may be designed for a single eye or both eyes adapted forstereoscopic display. In the case of HMD for both eyes, it is possibleto obtain a more natural image by providing an improved light quantitydistribution allowing easier fusion of left and right images.

In the above-embodiments, a virtual image observation system including avirtual image focus optical system 206 has been described, but this isnot essential. It is possible to apply the present invention to a directsee-type liquid crystal display apparatus not having such a virtualimage focus system. The use of a liquid crystal panel P is not essentialeither, and the present invention can also be applied to a displayapparatus not utilizing a liquid crystal. The bonding between theillumination device 211 and the lower polarizer 203 is not necessaryeither.

As described above, according to the above embodiments, a scatteringmember (or means) and a transparent sheet member are sequentiallydisposed contiguous to a light source, light emitted from the lightsource is better utilized by scattering and reflection at the scatteringmember, thereby providing a uniform light quantity distribution.

Further, in case where the sheet member is designed to have a refractiveindex n larger than a refractive index n' of a medium disposed on atransmitted light side of the sheet member, a portion of lighttransmitted through the sheet member at an angle lower than a certaincritical angle causes total reflection at the boundary between themedium and the sheet member, thereby further uniformizing the lightquantity distribution.

Further, in the case of disposing a prism device on the light emissionside of the sheet member, the light transmitted through (i.e., emittedfrom) the sheet member is provided with an improved directionality toincrease the light quantity emitted from the illumination device andentering the human eyes.

When the above illumination device is applied to a liquid crystaldisplay apparatus, it is possible to prevent the image qualitydegradation due to light quantity irregularity.

Further, the uniformization of the light quantity distribution can beaccomplished without using a filter having a non-uniform transmittancedistribution, so that it is possible to obviate the lowering in emittedlight quantity per se from the illumination device, the image qualitydegradation due to dark illumination, and a lower power efficiency.

Further, in the case of using an illumination device having a largerarea than a display device, it is possible to provide a further uniformlight quantity distribution and a further improved image quality.

(Sixth Embodiment)

FIG. 15 is a schematic sectional view of an optical system including adisplay apparatus (a liquid crystal view finder) according to a sixthembodiment of the present invention.

Referring to FIG. 15 showing a section of a y-z plane, the liquidcrystal display apparatus 301 includes a cold cathode lamp 302 as alight source, an inside reflection frame 303, polarizers 304 and 306 anda transmission-type liquid crystal panel 305. The optical system furtherincludes a virtual image focusing system 306 for guiding light flux 308from the liquid crystal display apparatus 301 to a human eye.

An illumination device (surface illuminant device) is constituted by thecold cathode lamp 302 and the inside reflection frame 303, and whitediffused illumination light is emitted from the illumination device inthe Z-direction and incident to a polarizer 304 as one of a pair ofpolarizers 304 and 306 arranged in cross nicols. By the polarizers,linearly polarized light is selectively formed and enters the liquidcrystal panel 305 comprising pixels arranged two-dimensionally. Whenpassing through the liquid crystal panel 305, the linearly polarizedlight is subjected to birefringence and then transmitted through theother polarizer 306 to be converted into a two-dimensional image havinga light intensity distribution.

In the case of the color liquid crystal panel, the liquid crystal panel305 is provided with a color filter (not shown) having color segmentscorresponding to the respective pixels. Of the light transmitted throughthe liquid crystal panel 305, only a portion within the aperture (shownas 2NA determined by an incident pupil and a focal length of the opticalsystem 307) on the panel 105 side of the optical system 307 is guided tothe eye 308.

In the case of a liquid crystal display panel, the transmitted lightcontrast distribution is provided with an asymmetrical anglecharacteristic (viewing angle characteristic) due to asymmetry of liquidcrystal director orientations, so that the optical system 207 maypreferably constitute a telecentric system for guiding principal rays ina direction (Z-direction) normal to the liquid crystal panel 305 surfaceas shown in FIG. 15.

In FIG. 15, the total aperture angle (=2 arcsin NA) is shown as 2NA.Depending on an illuminance at a retina of a human eye E, the pupil sizeof the eye E is changed to determine an effective light flux diameterentering the eye E and an effective NA for emission light from theliquid crystal panel P. As the brightness changes depending on the kindof image source and in order to facilitate the adjustment for alignmentof the optical axis of the optical system and the optical axis of theeye E, a light flux diameter of 6-8 mm may be required for a pupil of1-2 mm. For this reason, the illumination device 211 may be evaluatedwith a light flux corresponding to NA of the optical system 206.

FIG. 16 is a sectional view of a surface illuminant device (illuminationdevice) according to this embodiment. Referring to FIG. 16, the insidereflection frame 303 disposed contiguous to the cold cathode lamp 302has inside reflecting surfaces 311 provided with a reflection film forreflecting visible range light, so as to emit diffused illuminationlight 310 in the Z-direction.

More specifically, the inside reflection film 303 may be formed byinjection molding of a plastic material, such as acrylic resin orpolycarbonate resin, and inside surfaces thereof may be coated with afilm of a metal, such as aluminum or chromium, or a dielectric laminatefilm, so as to provide a mirror surface. Such an inside reflection frame303 may be adopted for mass production and produced stably andinexpensively.

The reflecting film can be further coated with a protective film of SiOor SiO₂, e.g., by vapor deposition, so as to increase the strength anddurability. Further, the plastic substrate thereof can be formedintegrally with a plastic member of the cold cathode lamp 302. This isadvantageous in reduction of number of parts, increasing the reliabilityand reducing the production cost. It is also possible to form the insidereflection frame 303 by directly machining a metal having a goodmachinability, such as brass or bronze, to mirror-finish the innersurface as in production of a polygonal mirror used in a laser beamprinter, while it may provide a somewhat increased weight. This isadvantageous in providing increased durability against, e.g., heat, sizeaccuracy and surface accuracy, and reduced change with time.

Further, it is also possible to form a mirror by bonding an aluminumfoil onto a thin plastic substrate, and cut and form the mirror into aninside reflection frame also functioning as a barrel for the liquidcrystal device. This may provide somewhat inferior surface accuracy andsize accuracy but may be advantageous in production cost.

FIG. 17 is a schematic sectional illustration (on a y-z plane in FIG.16) for describing a principle for providing an improved light quantitydistribution according to the illumination device of this embodiment.

Referring to FIG. 17, the upper surface of the cold cathode lamp 302forms a diffusion or scattering surface 320 and emits diffusion lighthaving a directional distribution determined by the structure of thecold cathode lamp 302 and the diffusion (or scattering) characteristicof the diffusion surface 320 in the Z-direction toward the liquidcrystal panel (not shown).

Of the diffused light from the cold cathode lamp 302, only a portionwithin 2NA of the optical system 307 shown in FIG. 15 is guided to theeye 308. In the central region of the cold cathode lamp, light rayswithin an angle formed between light rays 321 and 322 are guided to theeye. Actually, the light rays are within a three dimensional cone butare explained to be within a two-dimensional angle.

On the other hand, in a peripheral region, light rays between a lightray 324 and hypothetical light ray 323 can be guided to the eye 308, buta part of the cold cathode lamp emitting the hypothetical light ray 323is out of the end of the cold cathode lamp and is actually not present.Accordingly, the light quantity in such a peripheral region is caused toremarkably decrease in the case of a conventional illumination devicenot having the inside reflection frame 303.

In this embodiment of the illumination device (surface illuminantdevice) having the inside reflection frame 303, a light ray 326 goingoutside 2NA in a conventional device is reflected by the insidereflection frame 303 to form a reflected light ray 325 within 2NA toalleviate the light quantity decrease in the peripheral region.

Now, it is assumed that the inside reflection frame 303 has an insidereflection surface having a height h, the liquid crystal panel isdisposed at a distance z₀ from the diffusion surface 320, and thediffusion surface 320 has a size y₁. Further, a certain flux of lightrays including a central ray normal to the diffusion surface areconsidered so that the central ray is disposed at a distance y₀ from aperiphery, each ray has an angle a from the normal, and θ=arcsin NA. Inthe case where the inside reflection frame 303 is absent, a light fluxentering in NA of the optical system 307 within the light flux at aperipheral position yo entering the liquid crystal panel is determinedby angles a with respect to

left periphery: 0≦y₀ ≦z₀ ·tanθ

right periphery: y₁ -z₀ ·tanθ≦y₀ ≦y₁

as follows (when the angle α is taken positive in a clockwise rotationdirection about a normal to the liquid crystal panel):

left periphery: -θ≦α arctan (y₀ /z₀)

right periphery: -arctan((y₁ -y₀)/z₀)≦α≦θ,

thus showing that the light quantity is reduced as the positionapproaches the periphery.

On the other hand, in the case where the inside reflection frame 303 ispresent according to this embodiment, the light rays having an angledetermined as follows are guided within NA:

left periphery: -θα≦ arctan (y₀ /(z₀ -h) or θ

right periphery: -θ or -arctan((y₁ -y₀)/(z₀ -h))≦α≦θ.

Thus, it is shown that the decrease in light quantity at the peripheralregion is alleviated. It is also shown by the above formulae that ahigher degree of improvement can be attained as the reflection frameheight is set to be closer to the liquid crystal panel position z₀according to the NA of the optical system 307.

FIG. 18 schematically illustrates the effect of light quantitydistribution uniformization according to this embodiment. The abscissa yrepresents a lateral position on the illumination device having alateral size y₁, and the ordinate I represents a light quantity guidedwithin NA (three dimensional) of the optical system 307. A dashed line331 represents a light quantity distribution in a conventional casewhere the inside reflection frame 303 is absent, showing the lightquantity at the periphery decreases down to 30% of that at the centralregion. A solid line 330 represents an improved light quantitydistribution according to this embodiment, showing that the lightquantity at the periphery is recovered to 70% of that at the centralregion.

An identical effect is accomplished in the x-z plane so that the lightquantity distribution improvement according to this embodiment isaccomplished two-dimensionally, i.e., both in the x-axis and y-axisdirections.

(Seventh Embodiment)

This embodiment is directed to a surface illuminant device (illuminationdevice) provided with an improved uniformity due to an improvement indirectionality by adding a directionality controlling means.

FIG. 19 shows such an improved illumination device, wherein identical orlike parts are denoted by identical numerals. Referring to FIG. 19, aprism array 340 is disposed contiguous onto the diffusion surface 320,thereby improving the directional characteristic of the diffused lightin the y-axis direction in addition to the above-mentioned lightquantity uniformization effect according to the inside reflection frame303.

(Eighth Embodiment)

An eighth embodiment of the display apparatus according to the presentinvention is illustrated in FIG. 20 wherein identical or like parts aredenoted by identical numerals as in FIG. 15.

Referring to FIG. 20, the display apparatus 301 includes a liquidcrystal panel 307 and an illumination device (including the lamp 302 andthe reflection frame 303) designed to have a larger area than the imagedisplay region size of the liquid crystal panel 307, so as to utilizeonly a high light quantity uniformity region of light from theillumination device as illumination light. This results in a wastefulillumination device portion, a lower power efficiency and an increase insize and weight of the apparatus, but provides an ideal level of imagequality. Incidentally, a light shielding frame 341 is disposed so as toobviate stray light by cutting off unnecessary illumination. As aresult, it becomes possible to selectively utilize a region of thehighest uniformity of light quantity distribution through a lightshielding frame as illumination light, thereby providing extremely goodimage quality.

As the essential effect of the present invention is to obviate adecrease in light quantity at the edge or peripheral region of anillumination device. Accordingly, the use of a reflection frame havingfour reflection surfaces is not necessary. For example, the case of onereflection surface is also effective in alleviating the light quantitydecrease at the corresponding edge or peripheral region to provide abetter light quantity distribution.

As described with reference to FIG. 17 and mathematical formulae, it ispossible to modify the height h or the position in x-axis and y-axisdirections of the reflection frame or surface 303, so as to effect anoptimization corresponding to the display apparatus used. Regarding anarrangement in z-axis direction, the reflection frame 303 need not be incontact with the diffusion surface 302 but can be spaced from thediffusion surface 302, thereby to still exhibit some effect.

In the above embodiments, the reflection frame has been explained tohave a reflection surface almost perpendicular to the diffusion surface302, but it is possible to incline the reflection surface(s) withrespect to the diffusion surface so as to control the light dispensingcharacteristic and guide the illumination light in a desired directiondepending on the required light dispersing characteristic and NA, thuseffecting a uniformization of light quantity distribution in a broadersense. For example, it is possible to set different inclination anglesfor four reflection surface, e.g., so that the opposite inner surfacesare parallel, or inwardly inclined or outwardly inclined in the lightemission direction, so as to be suitable for providing a desired lightquantity distribution.

As described above, according to the present invention, it is possibleto provide an illumination device (surface illuminant device) having animproved two-dimensional light quantity distribution and a highuniformity of light quantity distribution.

Further, according to the present invention, it is also possible toprovide an illumination device with an improved light quantitydistribution, particularly in one of two-dimensional directions, i.e.,with a one-dimensionally high uniformity of light quantity distribution.

Further, according to the present invention, it is also possible to usea light-shielding frame, so as to select a particularly high uniformityregion of light quantity distribution thereby providing a betteruniformity of illumination light quantity distribution.

The illumination device according to the present invention may suitablybe combined with a display device having a light-shielding filmcomprising a dark-colored organic resin (i.e., so called black matrix(BM)) between color filter segments, because the reflected light fromthe light-shielding film (BM) portion than in a display device using aninorganic black matrix of, e.g., chromium. As a result, it becomespossible to provide an improved contrast in the peripheral region on thedisplay surface.

What is claimed is:
 1. A display apparatus, comprising:a liquid crystaldisplay device for image display, a backlight having a light emissionsurface for emitting light for illuminating the liquid crystal displaydevice, and a reflection member having a size conforming to an outerframe of the liquid crystal display device and disposed insertablybetween the liquid crystal display device and the backlight, thereflection member having an inner reflection surface perpendicular tothe light emission surface of the backlight.
 2. A display apparatus,comprising a liquid crystal display device for image display, abacklight for illuminating the liquid crystal display device, areflection member having a size conforming to an outer frame of theliquid crystal display device and disposed insertably between the liquidcrystal display device and the backlight, and a support and controlmechanism for supporting the reflection member so as to allow a movementof the reflection member and controlling a position of the reflectionmember.
 3. A display apparatus according to claim 2, further comprisinga position sensor for detecting a position of a unit composed of theliquid crystal display device and the backlight, a control circuit forsupplying a control signal to the support and control mechanism so as tocontrol a position of the reflection member, and a backlight supportmember for supporting the backlight in proximity to the liquid crystaldisplay device.
 4. A display apparatus according to claim 3, whereinsaid position sensor, said control circuit and said reflection membersupport and control mechanism function to provide a first state whereinsaid reflection member is inserted between and parallel to the liquidcrystal display device and the backlight and in alignment with the outerframe of the liquid crystal display device, and a second state whereinsaid reflection member retracts from between the liquid crystal displaydevice and the backlight and the backlight is moved to a close proximityto the liquid crystal display device.
 5. A display apparatus, comprisingat least two display apparatuses each according to claim 4, said twoapparatuses being disposed laterally with respect to each other.
 6. Adisplay apparatus according to claim 5, wherein, in each of said atleast two display apparatuses, the reflection member assumes said firststate when the unit of the liquid crystal display device and thebacklight is at a first position and said second state when the unit isat a second position different from the first position, and the units inthe respective display apparatuses are moved in association with eachother.
 7. A display apparatus according to claim 1, wherein the lightemission surface of the backlight is planar.